1. Field of the Invention
The invention relates to a method for purifying biomass syngas under a negative pressure.
2. Description of the Related Art
Like coal gas production, the biomass gas production requires purification processes of cooling and washing. The temperature of the crude coal gas from a carbonization furnace is at 650° C. while the temperature of the syngas at the outlet of the gasifier is higher than 1000° C. Thus, it is desired to develop an innovative cooling method for biomass syngas.
Conventional means for preliminary cooling the coal gas include: indirect preliminary cooling, direct preliminary cooling, and indirect-direct preliminary cooling. The preliminary cooling mainly means that the coal gas is cooled to a temperature of between 22 and 35° C. after flowing out of the carbonization furnace and before entering an electric tar precipitator.
Methods for removing dust from coal gas include: precipitation, filter, cyclone, electric precipitation, water washing, and dust removal by Venturi scrubber. Different dust removal methods vary in the dust removal effect and the resistance consumption.
Characterized in complicate system, long procedure, high energy consumption, low efficiency and stability, and being uneconomic, the conventional methods for coal gas purification must be optimized and developed when it is applied to treat the biomass syngas.